PubMed · 5914460
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R F Wells. 1966. Scrub typhus.. https://pubmed.ncbi.nlm.nih.gov/5914460/
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The extensive use of chloramphenicol (CAP) in livestock leads the accumulation of CAP in livestock manures, threatening environmental and human health. Therefore, eliminating or reducing CAP concentration in manures before its re-utilization and application through microbial remediation is necessary. Exiguobacterium sp. CAP4, isolated from the plastisphere in duck manures, was capable of degrading CAP with the biodegradation efficiency of 97.8 % at initial CAP concentration of 5 mg/L within 4 days. A total of twenty-four biotransformation products were determined, including two novel transformation products, TP166 and TP203, enriched the integrity of CAP biodegradation pathways. Furthermore, the biotransformation process was proposed as a detoxifying process through biotransformation products toxicity evaluation. Notably, Exiguobacterium sp. CAP4 successfully colonized in the cow manures after inoculation, and bioaugmented the biodegradation of CAP in virgin cow manures. This study significantly extended our understanding of the CAP biotransformation fate, and provided a promising bacterial strain for bioremediation of CAP containing wastewater in situ.
The scale of negative DNA supercoiling generated by transcription in Top(+) Escherichia coli cells was assessed from the efficiency of cruciform formation upstream of a regulated promoter. An increase in negative supercoiling upon promoter induction led to cruciform formation, which was quantitatively measured by chemical probing of intracellular DNA. By placing a cruciform-forming sequence at varying distances from the promoter, we found that the half-dissociation length of transcription supercoiling wave is approximately 800 bp. This is the first proof that transcription can affect DNA structure on such a remarkably large scale in vivo. Moreover, cooperative binding of the cI repressor to the upstream promoter DNA did not preclude efficient diffusion of transcriptional supercoiling. Finally, our plasmids appeared to contain discrete domains of DNA supercoiling, defined by the features and relative orientation of different promoters.
The destruction of Escherichia coli M23 OR.H- using lethal water activity levels and nonlethal temperatures was investigated. Death rates were measured for a combination of four growth-permissible temperatures (15 degrees C, 25 degrees C, 40 degrees C and 45 degrees C) and four distinctly lethal water activities (0.75, 0.83, 0.88 and 0.90). In addition, death rates were measured at two temperatures (4 degrees C and 50 degrees C) outside the growth range of E. coli. Death rate increased both at higher temperature or lower water activity. Inactivation curves resulting from exposure of E. coli to osmotic stress were biphasic. The initial rate of death was followed by a slower second phase decline, or "tailing" effect. Addition of chloramphenicol to the suspending medium reduced the tailing effect and suggested that tailing was caused by de novo protein synthesis.